Separation and detection of an analyte, such as a macromolecule, protein, protein fragment, polymer, biomolecule, biopolymer, biological cell, a small molecule or other molecular complex has widespread application in fields such as genomics, proteomics, drug discovery, medical diagnostics, environmental sensing, pollution monitoring, detection of chemical or biological warfare agents, and industrial process monitoring. One common technique used to separate analytes such as proteins, polymers, biomolecules and other macromolecules based on size is size-exclusion chromatography (SEC). Analysis using SEC is usually performed by elution of the analyte solution of interest along the appropriate porous stationary phase and detection of the separated products at the end of the column using for example ultraviolet (UV) absorption, refractive index changes, or mass spectroscopy. However, the time scale associated with SEC experiments is such that analytes comprising weakly bound complexes typically cannot be characterized in this fashion because weakly bound complexes will typically dissociate and rather than characterizing the analyte, the constituent amino acids or other constituent molecules will be characterized. SEC is susceptible to other drawbacks, such as its complicated calibration, its slowness and inefficiency, and its rather large scale, which leads to a wasteful use of expensive, hazardous and environmentally troublesome solvents. SEC itself is a lengthy process, and since SEC only measures hydrodynamic volume, a further subsequent process is necessary to detect and identify the specific molecule, which unduly lengthens the procedure.
Conventional methods for fabricating Si nanostructures that may subsequently be used in separating and detecting applications have presented drawbacks as well, namely that pore size, configuration and distribution have been difficult to control, predict and reproduce. Reducing or eliminating these drawbacks has advantages in numerous applications as well. For example, in controlled release of a pharmaceutical, the drug of interest is usually infused in a porous material that slowly releases the drug at a rate that is therapeutically relevant. Many porous materials have been used, including porous Si, polymers such as poly(lactide), liposomes, and porous silica glasses. The release rates are dependent on many parameters, among which parameters is pore size in the host material. In some cases it is desirable to tailor the release characteristics to follow prescribed dose-time characteristics, and conventional methods have proven unsatisfactory in this respect.